Mammalian cell biology 5

• what do transport vesicles do

  deliver their content between compartments and the plasma membrane 
• how big are transport vesicles

  25-200nm
• what are the most prominent transport vesicles

  vSNAREs
• why are vesicles coated

  • the coat concentrates specific proteins in patches
  • the coat moulds the forming vesicle
  • coats are specific for particular places in the endocytic and the exocytic pathway
• process of clathrin coated vesicle formation

  1. specificity is provided by the adapter-receptor interaction
  2. coat formation curves the membrane and shapes the vesicle
  3. the coat gets rapidly lost and the vesicle interacts with the cytoskeleton for intracellular transport
• what do extracellular vesicles transport

  RNAs and proteins, provided by the donor cell
• what are extracellular vesicles

  transport vesicles released from cells
• where are extracellular vesicles found

  • body fluids
  • fluids around brain and spinal cord
  • urin
  • blood
• how big are microvesicles

  500-1000nm diameter
• where are microvesicles formed

  at donor plasma membrane
• what do microvesicles transfer

  • proteins, mRNAs and miRNAs
  • that control protein expression
• how big are exosomes

  40-100nm diameter 
• where are exosomes formed

  at early endosomes, released from late endosomes (multivesicular bodies)
• what do exosomes transfer

  • proteins, mRNAs, miRNAs
  • that control protein expression
• role of exosomes and microvesicles in immunology

  modulation in lymphocytes and macrophages in the heart and vessels
• role of exosomes and microvesicles in blood

  stimulation of coagulation, blood vessel formation and thrombosis
• role of exosomes and microvesicles in CNS

  integration of neurons and various gial cells types, control of synaptic function, neuronal plasticity, neuronal-glial cell communication and myelination 
• role of exosomes and microvesicles in bone

  modifying enzyme activity 
• what are peroxisomes

  • single-membrane bound organelles that contain many enzymes (crystalline core)
  • major sites of oxygen utilisation (similar to mitochondria)
• how many different enzymes do mammalian peroxisomes contain

  >50 and over 20 peroxins that mediate import 
• what does detox of peroxisomes generate

  H2O2
• what part of lipid metabolism are peroxisomes involved in

  biosynthesis of cholesterol and breakdown of long chain fatty acids (B-oxidation)
• what are glyoxysomes

  peroxisomes in plant seeds that convert fats into sugar
• formation of peroxisomes

  1. vesicles containing peroxisomal membrane proteins leave Golgi
  2. import of peroxisomal proteins (SKL)
• where are lipid droplets made

  smooth endoplasmic reticulum
• what does FABP do

  fat-acid-binding protein (FABP) makes fatty acid water soluble (they shield the fatty acid by binding it in a hydrophobic pocket)
• cytoskeleton definition

  the cytoskeleton consists of filamentous bio-polymers (microtubules, f-actin and intermediate fibres) and of associated proteins that are modulating the activity, dynamics or organisation of the cytoskeleton (actin binding protein)
• features of the cytoskeleton

  • connects all parts of the cell
  • supports motility
  • helps spatial organisation
  • provides tracks for intracellular trafficking
  • provides stability to the cell
• how big is f-actin

  7-9nm
• functions of f-actin

  short range transport

  cell migration
• how big are microtubules

  25nm
• functions of microtubules

  • long range transport
  • chromosome inheritance
• size of intermediate fibres

  10nm
• function of intermediate fibres

  mechanical strength